There have been numerous attempts in the past to provide state-of-charge or battery condition indicators which allow users to readily determine the state-of-charge of storage batteries, particularly those used in automobiles. These attempts have ranged from the extremely simple to very sophisticated, and representative examples found in the patent literature include the following U.S. Pat. Nos. 964,995; 3,061,827; 3,408,973; 4,289,836; 4,625,175; 5,130,659; and 5,159,272.
There remains a need, however, for a low cost, reliable state-of-charge indicator which is both easy to use and easy to manufacture. It is the principal object of this invention, therefore, to provide an easy to use and reliable state-of-charge indicator which, in the exemplary embodiment, is incorporated directly within the cover of a lead acid battery of the types used in automotive and marine applications.